Former National Geographic editor Martin delivers the reverse of his Secret Heroes, highlighting Americans who have negatively impacted society in a variety of stomach-churning ways. He sets the tone with his profile of the rapacious Rhode Island slave trader James DeWolf, whose considerable wealth is something with which his heirs continue to struggle, and Samuel Mason, a vicious pirate captain who terrorized travelers along the Ohio River in the early 1800s. There’s also Belle Sorensen Gunness, the icy Norwegian immigrant who “is believed to have slain over 40 people, including her two husbands and all seven of her children”; Charles Davenport, who campaigned for racial purity and helped popularize eugenics; and the notorious Ed Gein, the reclusive Wisconsin serial killer who was the inspiration for several movie murderers. Martin’s rich and varied portraits display misbehavior, from simple idiocy and apathy to conniving con men, gold diggers, and gamblers. He also includes inveterate hucksters like Don Lapre, the late-night TV pitchman whose infomercials and Ponzi schemes yielded a tidy sum he eventually lost (along with his life; he committed suicide in jail while awaiting trial). They make a pretty reprehensible bunch, but Martin puts their crimes in context while keeping the book entertaining and informative. (Mar.)